1. Field of the Invention
The invention relates to a method of making a screen cylinder, in which method mesh wires are arranged next to one another at predetermined intervals and attached in the axial direction of the screen cylinder to provide a cylindrical mesh surface on the inside of ring-shaped supporting rods, and at least some of the supporting rods are surrounded on the outside with supporting rings that support them.
The invention also relates to a screen cylinder for purifying and sorting out a pulp mixture, the screen cylinder comprising mesh wires arranged in the axial direction of the screen cylinder at predetermined intervals to provide a cylindrical mesh surface, the mesh wires being attached to the surrounding supporting rods, and at least some of the supporting rods being surrounded on the outside by a supporting ring.
2. Description of the Prior Art
Screen cylinders are made by attaching parallel mesh wires that provide a mesh surface next to one another in a cylindrical shape at desired intervals. This is usually done by welding or brazing the wires to the supporting rods; this is difficult, and the welding also produces flashes. In addition, the welding produces stress on the perimeters due to different thermal expansion and shrinkage. Another problem is that the screen cylinder requires a supporting structure in which the separate supporting rings are usually welded to the supporting rods to provide a uniform structure. As a result, the varying pressure and mechanical load put stress on the inside of the cage during the use, and the stress, which is distributed over the radially extending area formed by the supporting ring and the mesh wire, may cause the structure to crack. This is particularly evident in a solution where the mesh wires are welded to the supporting rods.